Light source



1942- .1. R. STIRNKORB LIGHT SOURCE Filed July 22, 1940 1NVENTOR.

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ATTORNEYS.

Patented Oct. 6, 1942 EEEQE.

LIGHT SOURCE John R. Stirnkorb, Cincinnati, Ohio, assignor to ScienceLaboratories, Inc., Norwood, Ohio, a

corporation of Ohio Application July 22, 1940, Serial No. 346,819

1 Claim.

My invention relates to light sources of elongated shape and employingan arc struck between interspaced electrodes in an ionized atmosphere.Long, tube-like lamps of the class referred to have hitherto beendeveloped for many purposes including, but without limitation, theproduction of ultra-violet radiation for therapeutic, bactericidal oractivation work; and fluorescent type tubes are now coming intoincreasing use for illumination, wherein ultra-Violet radiationgenerated by an arc impinges upon a coating of fluorescent substances onthe inside of the envelope and produces visible light.

My invention relates primarily to the solution of a problem whichbecomes most pronounced in long tube-like light sources, used in ahorizontal position, and in which the atmosphere is a relatively highpressure atmosphere. The are discharges in lamps become relatively thickand relatively cooler as the pressure of the ionized atmosphere islowered, tending ultimately toward a glow discharge. In high pressurelamps, however, the arc becomes thin and intense and de velopscomparatively great heat. When such lamps are used horizontally, theretends. to be a bowing of the are which in extreme instances may permitthe arc to touch the sides of the envelope. Under these circumstances,the life of the light source is imperiled because the envelope may melt.It is an object of my invention to overcome these disadvantages, toprovide means for keeping, particularly, a thin and intense arc awayfrom the nvelope, and to prolong the life and safety of use of the lightsource.

These and other objects of my invention which will be set forthhereinafter or will be apparent to one skilled in the art upon readingthese speci Fig. 3 is a transverse sectional view taken along I thelines 33 of Fig. 1.

Fig. 4 is a partial longitudinal section of a light source showing amodified form of my arc centering means.

Fig. 5 is a transverse sectional view related to Fig. 4 and showing aface View of the centering means.

Fig. 6 is a partial longitudinal section illustrating both another typeof arc centering means and. a mode of mounting it in a lamp structure.

Fig. 7 is a view, with parts in section of yet another embodiment oftheinvention.

I shall not herein describe with particularity the various forms oflight source construction to which may invention may be applied. Theeffectiveness and utility of the invention is not dependent upon thenature of the electrodes, the nature of the starting means embodied inconnection with the light source, or the manner in which ionization isstarted in the atmosphere. For a complete description of one form ofstructure to which the present invention is well adapted, I refer to mycopending application entitled Light sources, Serial No. 345,807, filedJuly 16, 1940.

In connection with the problem to the solu-' tion of which my inventionis addressed, I have discovered that a thin, intense arc may beprevented from bowing to the extent ofv striking the envelope, evenwhere the envelope .is very long and thin, if the arc is centered in theenvelope at one or more places between the electrodes.

1 have further discovered that the arc may be so centered by placing inthe envelope one or more are centering devices comprising walls havingcentral perforations. The number and spacing of arc centering meansbetween the electrodes in any given lamp may be varied in accordanceboth with the length of the lamp and with the diameter of its envelope;but I have discovered that if the arc is centered at frequent enoughintervals, the amount of bowing of the are between the points at whichit is centered can be controlled in such a way as to make sure that thearc will not come into contact with the envelope under any conditions ofuse. I have further discovered the surprising fact that the arc willseek a central perforation in a baffle or arc centering means inpreference to any outlying passageway which there may be.

Referring to Fig. 1, l indicates the envelope of a light source havingbases 2 and 4 at either end. Electrode means, comprising wires 5 and 6or 7 and 8, as the case may be, pass through presses in the ends of theenvelope and are connected respectively with contact prongs 9 and It OrI I and tion, depending upon the use to which th light source is to beput. The envelope may carry on its inside a coating of fluorescentsubstance.

In Fig. 1 for centering the arc, I provide midway between the arcelectrodes 5, 6 and 1, 8, a baflle means l having a central perforationI6. This baffle means may be a disc of any material substantially shapedto fit the interior of the tube l and, in this embodiment fusible to theglass or capable of adhering to fused glass. During the assembly of thelight source, while the disc I5 is held in position, the tube l is fusedto the disc at intervals as shown at I! by local application of a fusingflame.

The disc or bafile may be made of a wide variety of substances. Ordinaryglass, Pyrex glass, or any of the special glasses may be employed; but Ihave also used such materials as ceramics, quartz, carbon, mica andmetals. Due to the intense heat of the are a relatively high meltingpoint material is desirable. However, it is not necessary that thebafile be entirely unaffected by the heat of the arc. A perforated glassdisc, for example, may tend to bead about the edges of the perforationand gradually the perforation may tend to become somewhat enlarged.However this action occurs so slowly as compared with the normal lengthof life of the light source as to make the use of glass substances quitefeasible.

I have encountered no difficulties of mechanical character in connectionwith the use of baffle means. Where the baflie is to be interfused withthe envelope or where the glass of the envelope is to be softened andpressed about the edges of the baffle member so as to hold it, I may dothis entirely around the circumference of the tube; but I have not foundit necessary. Sufficient shaping or interfusion to hold the baffle isall that is required, and I find that if interspaces, as indicated at I8 in Fig. 3, exist between the periphery of the disc and the internalcircumference of the envelope, these interspaces have no effect on theoperation of the baffle. This is for the reason indicated above, namely,that the arc seeks the central perforation and passes therethrough inpreference to any outlying channels of communication.

This fact among others makes possible the use of baflie means such asillustrated in Figs. 4 and 5. Here I have shown a metallic disc orwasher l9 centrally perforated at 20, and about its periphery providedwith feet 2|, alternate ones of which are bent in opposite directions.These feet engage the interior of the tube and the fit may be snugenough to make it unnecessary otherwise to retain the position of thebaflie. The bending of the feet in opposite directions provides arelatively broad peripheral bearing for the baffle and preventsdisplacement of the bafiie by tilting.

In no instance have I encountered any difficulty arising from theheating of the baffle by the arc and differential rates of contractionand expansion of the envelope and the baffle. This is true not only ofthe non-metallic and/or refractory materials which I may employ, but itis true also in the case of metal. While undoubtedly heat is transmittedto the envelope'by the baffle, the rate of conduction of heat away fromthe joint by the envelope and the rate of loss of heat to th surroundingair seems sufficient to prevent any difficulty in actual practice.

Another mode of aflixing a baffle or are centering means is shown inFig. 6. Here the envelope 22 has been peripherally bowed as at 23 toprovide a groove on the inside of the envelope. Relatively thin andbendable or resilient baffle means 24, perforated as at 25, may be bowedto permit its insertion in the tube and allowed to spring outwardly inthe internal groove 23 much as a crystal is installed in a watch.

In Fig. 2 I have shown the use of a plurality of interspaced bafllemeans 26, 21 and 28 in a light source embodying a tube 29 which isrelatively very long and thin. It will easily be within the skill of theworker in the art to determine the number of bafiles or are centeringdevices he will need; but it may be noted that the length of the arc isnot the only criterion. The relative diameter of the tube or envelopemust be considered and also the nature of the arc itself as determinedby the nature and pressure of the atmosphere as well as the degree ofbowing of the are encountered in view of these factors.

In Fig. '7 I have shown yet another structure for the purpose whereinthe envelope 26 is provided internally with one or a plurality of bafllemembers having tubular bodies 21', and end flanges 28, shaped to conformgenerally to the interior of the envelope. Where the tube-like bafiiesare short in length, they may be made of opaque substance, for exampleceramics, or metal. But a single, long tubular means may be employed tokeep the arc away from the envelope. Where this is done, the tubularmeans must, of course, be transparent or translucent, and in ultravioletdevices, should be pervious at least to the desired wave lengths of theultraviolet spectrum. Also, by reason of its close proximity to theintense are, it should be heat resistant. Thus quartz, or heat resistantglass should be used. In the use of such tubes within an envelope,however, considerable savings may be made over the manufacture of thewhole lamp of quartz or heat resistant glass. The tube may be coated onits outside surface with fluorescent substances, and may be so coatedbefore the tube is placed in the envelope.

The tube or tubes are preferably anchored to the envelope as at 29 toprevent displacement.

It will be within the skill of the worker in the art moreover to applymy teachings to light sources of different character than the specificones here illustrated. Modifications may be made in my invention withoutdeparting from the spirit of it.

Having thus described my invention what I claim as new and desire tosecure by Letters Patent, is:

In a light source, an envelope, arc electrodes in an ionizableatmosphere therein, and at least one means in said envelope intermediatesaid electrodes for centering said arc, said means comprising aperforated disc extending substantially across the breadth of saidenvelope, said disc being a disc of metal, the edge of said disc beingformed into divided tongues, and said tongues alternately beingangularly bent, some in one direction and some in another so as toengage the inner surface of said envelope and form a bearing therein atinterspaced points to preclude the tilting of said disc, the fit of thetongued disc in said envelope being sufficiently snug to minimizemovement of said disc longitudinally of said envelope.

JOHN R. STIRNKORB,

